I. Field of the Invention
The present invention relates generally to gas appliances and, more particularly, to a retrofit drive orifice for use with such gas appliances.
II. Description of the Prior Art
Conventional gas appliances, for example, gas furnaces, water heaters and the like, include a burner coupled to a source of flammable gas, typically natural gas, via a manifold.
In order to limit or restrict the flow of gas through the manifold and to the burner, these previously known gas appliances have employed orifices attached to the manifold and having a restricted fluid passage through bore. In order to secure the orifice to the manifold, external threads are formed about one end of the orifice which threadably engage internal threads in a hole through the manifold.
This previously known means for attaching the orifice to the manifold, however, is disadvantageous when replacement and/or retrofit of the orifice is desired. Such replacement and/or retrofit of the orifice may be required, for example, when further restriction of the orifice is desired in order to reduce the fuel consumption of the gas appliance for energy conservation purposes. Many gas appliances, particularly gas furnaces, have oversized orifices which are wasteful of natural gas.
These previously known orifices for gas appliances, however, have not been produced with standard thread sizes. Consequently, it is rarely possible to merely unscrew the old orifice and to screw in a new orifice with the desired through bore. Moreover, when the old orifice is unscrewed, the seal between the orifice and manifold is broken and the new orifice oftentimes forms an inadequate seal with the manifold. An inadequate seal, in turn, results in gas leaks and the resultant safety hazard.
As a result of this lack of standardization for the orifice thread sizes, it has been the previously known practice when installing a new orifice into a gas appliance, to unscrew the old orifice and thereafter tap or thread a new hole corresponding to the thread size of the replacement orifice. This procedure, however, is disadvantageous in that it is time consuming, it requires special tools, and, therefore, it is expensive in labor cost.